GEAR SHIFTING POWER TOOL

Description

[0001] This invention relates in general to the field of gear shifting devices, more particularly to a gear shifting power tool.

[0002] Power tools such as nut runners, drills, grinders, sanders, or similar type tools provide a rotating shaft at a given speed and torque. Depending on the function being performed, it is often advantageous to provide a rotating shaft at different speeds and different torques. The speed and torque of a rotating shaft may be altered through the use of gears.

[0003] When using a power tool to rotate a fastener, it is often desirable to rotate the fastener at a high speed throughout the fastening process until the fastener is almost tightened or otherwise meeting with additional resistance. During final tightening or increased resistance, it is often advantageous to apply a low speed rotation with a higher torque. The speed and torque of a rotating shaft in a power tool may be altered by engaging and disengaging various gears. The engaging and disengaging of gears for changing the speed and torque of the rotating shaft may be accomplished through clutch members operable in response to fluid pressure.

[0004] Disadvantages of known speed shifting mechanisms may include component deterioration, jammed parts and frequent maintenance. Some types of speed shifting devices used in power tools do not provide for an adjustable torque setting. Other disadvantages with gear shifting power tools may include using fluid driven clutch members for engaging and disengaging gears that tend to be expensive, less reliable, and maintenance intensive. Other disadvantages may include shifting a power tool from a relative high speed/low torque rotation to a relative low speed/high torque rotation without a mechanism or means to ensure that the power tool will maintain the low speed/high torque condition so that proper tightening may be applied or so that a proper or desired torque may be applied. Additionally, some devices require two motors in order to achieve the high torque needed for a final tightening; one motor may rotate the output for a high speed/low torque output while another motor is added to achieve the high torque needed for final tightening.

[0005] US-A-3696871, which is considered to represent the closest prior art, discloses a rotary pneumatic torque tool such as a non-impacting nut runner, a screw driver or like tool, having means for automatic torque shift between a motor unit and a output shaft, the motor unit including a speed reducing gear having one or more reduction gear steps, a clutch sleeve member drivingly connected to the last gear step for transmitting high torque, an output shaft coaxial with and rotatably mounted relative to said clutch sleeve member and connectable to means for engaging a workpiece, said output shaft being rotatably mounted in an internal central bearing provided in the clutch sleeve member, an input or driving shaft coaxially and rotatably journalled relative to said clutch sleeve member and connected to the motor unit and a point preceding the last gear step for transmitting low torque, a torque transmission limiting coupling provided between said driving shaft and said output shaft. The automatic torque is obtained in response to the torque required for rotating a threaded member to be fastened, whereby the threaded member is first rotated at high speed and low torque and, when a predetermined reaction torque at the threaded end is exceeded, at low speed and high torque to reduce the total time for securing the threaded member.

[0006] According to the present invention, there is provided a rotatably-driven, torque-responsive, gear shift device for use in a power tool, the gear shift device comprising:

a drive spindle having an axis, a first end, a second end, and a partially hollow interior volume, the drive spindle being able to input, in use, a rotational force from a motor;

a drive clutch member drivably engaged to the drive spindle and movable along the axis of the drive spindle;

a biasing means between the drive spindle and the drive clutch member allowing, in use, an axial movement of the drive clutch member relative to the drive spindle when the biasing load of the biasing means is overcome;

a plunger positioned within the partially hollow interior volume of the drive spindle and movable, in use, towards the second end of the drive spindle to engage the drive clutch member when the drive clutch member has axially moved relative to the drive spindle for changing the gearing of the gear shift device;

a reset biasing means for biasing the plunger in the partially hollow interior volume of the drive spindle away from the second end to move the drive spindle away from the second end when the gear device is not in use; and

an inertial device coupled to the drive spindle such that, in use, it urges the plunger towards the second end of the drive spindle in response to rotation of the drive spindle.

[0007] According to another aspect of the present invention, there is provided a method for shifting gears, in response to an applied resistive torque, from an output rotational motion having relative high speed and low torque to an output rotational motion having relative low speed and high torque, the method comprising the steps of engaging a drive clutch member to a driven clutch member where the drive clutch member has an inner axial groove and is drivably engaged to a drive spindle having a plurality hollow interior volume, a first hole, a second hole, a first end, and a second end; biasing a plunger longitudinally away from the second end of the drive spindle where the plunger is positioned in the partially hollow interior volume of the drive spindle and contains a first tapered end and a second tapered end; rotating the drive spindle with a motor; applying a radially inward force to a first ball tending to force the first ball radially inward through the first hole towards plunger to provide a longitudinal force on the plunger opposite the biasing applied to the plunger in the step of biasing a plunger longitudinally; applying a torque to the drive spindle that resists the rotation of the drive spindle produced by the motor; disengaging the drive clutch member from the driven clutch member in response to the step of applying a torque to the drive spindle that resists the rotation of the drive spindle by compressing a spring between the drive clutch member and the drive spindle so that the drive clutch member moves longitudinally away from the driven clutch member and the inner axial groove positions over the second hole in the drive spindle; moving the plunger longitudinally towards the second end of the drive spindle in response to the step of applying a radially inward force on the first ball and the step of disengaging the drive clutch member form the driven clutch member; and forcing a second ball radially inward through the second hole of the drive spindle and into the inner axial groove of the drive clutch member in response to moving the plunger longititudinally towards the second end of the drive spindle.

[0008] Technical advantages of the present invention include allowing the use of lower revolutions per minute or lower rpm motor to drive a gear shifting device as compared to many prior art power tools. Another technical advantage may include that the invention typically allows the use of an oil-free motor running at a lower rpm and using less horsepower yet still delivering the desired output speed and torque. When the motor driving the gear shifting power tool is a pneumatic motor or air driven motor, advantages are realized by a reduction in air consumption and hence reduced noise levels and cost.

[0009] Other technical advantages include adjustable automatic shifting from an output having high speed/low torque to an output having low speed/high torque. The torque at which gear shifting occurs may be adjusted based on adjusting the biasing means for applying a force between the drive spindle and the drive clutch member. Other technical advantages of the present invention may include the reduced size and weight of the gear shifting power tools according to one embodiment of the invention because of self-contained operation.

[0010] Additional technical advantages of the present invention may include increased responsiveness to applied torques because of the absence of any external fluids needed for applying pressure to engage and disengage clutch members. Other technical advantages also include low speed/high torque operation without accidental reengagement of the clutch members because the invention ensures that the gear shifting power tool will stay in a low speed/high torque condition until all rotation stops.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a perspective view of a power tool according to one aspect of the present invention;

FIGURE 2 is a cross-sectional view, with portions broken away, of a power tool according to one aspect of the present invention shown in a high speed/low torque or engaged mode;

FIGURE 3 is a cross-sectional view, with portions broken away, of the inertial device of the power tool of FIGURE 2;

FIGURE 4 is a cross-sectional view, with portions broken away, of the power tool of FIGURE 2 except shown in a low speed/high torque or disengaged mode;

FIGURE 5 is a cross-sectional view, with portions broken away, of the inertial device of the power tool of FIGURE 4;

FIGURE 6 is a schematic view of a ball screw interconnection between a drive spindle and a drive clutch member which may be included as an aspect of the present invention;

FIGURE 7 is a perspective view of the ball screw keyway on the drive spindle of FIGURE 6; and

FIGURE 8 is an angled cross-sectional view of the drive spindle of FIGURE 7 taken along line 8-8 in FIGURE 7.

DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention and its advantages are better understood by referring to FIGURES 1-8 of the drawings, like numerals being used for like and corresponding parts of the various drawings. The invention may be used with or as a unique redesign of any number of power tools such as the power tools described in U.S. Patent No. 4,359,107, entitled "Shut-Off Apparatus for Pneumatic Driven Tools". It should be understood that the invention is applicable to other power tools as well. The FIGURES only illustrate one embodiment of the present invention. The environment and components of the embodiment will first be presented and then its operation.

[0013] FIGURE 1 illustrates power tool 10 with a casing 13 and including a rotatably-driven, torque-responsive, gear shift device in accordance with the present invention. Power tool 10 includes handle 12 for gripping, on/off switch 14 for controlling the input power to power tool 10, tool body 16, and right angle head 18 including output drive 20. Output drive 20 provides output rotational motion to an output attachment (not shown) that may grip a fastener or other item to be acted on by tool 10.

[0014] FIGURE 2 is a cross-sectional view, with portions broken away, of rotatably-driven, torque-responsive, gear shift device 30 showing drive clutch member 32 engaged to driven clutch member 34. This illustrates the engaged mode of gear shift device 30, which is the mode having relative high speed/low torque. Drive clutch member 32 has an inner axial groove 36 and is drivably engaged to drive spindle 38. Inner axial groove 36 could also be a slot or multiple slots positioned to receive a corresponding ball or balls when drive clutch member 32 disengages from drive clutch member 34. Drive spindle 38 has a first end 66 and a second end 68. Second end 68 of drive spindle 38 may serve as a pinion for a plurality of gears, or gear set, such as shown by pinion gear 70. First end 66 may be coupled to motor drive 86 for providing rotational motion thereto when energized.

[0015] Drive clutch member 32 is drivably engaged to drive spindle 38 through ball screw arrangement 64. See also FIGURES 6-8. Drive clutch member 32 has clutch dogs 80 for engaging driven clutch member 34. Drive spindle 38 and drive clutch member 32 may be biased away from each other by any biasing means, e.g., torque spring 40. Torque spring 40 is longitudinally positioned between drive spindle 38 and drive clutch member 32. Torque spring 40 couples to drive clutch member 32 by thrust bearing 82 and thrust race 84. Torque spring 40 may be coupled to drive clutch member 32 through any arrangement providing equivalent coupling. Torque spring 40 couples with drive spindle 38 through adjustment nut 42. The compression on torque spring 40 may be varied through the positioning of adjustment nut 42. Torque spring 40 may be sized to preference. Drive spindle 38 has first hole pair 44 and second hole pair 46 and a partially hollow interior volume 52. The two holes of first hole pair 44 may be spaced 180 degrees from one another on drive spindle 38 as shown in the embodiment of FIGURE 2. This is also true for the two holes of second hole pair 48. The present invention allows spacing of each hole around drive spindle 38 at any angle or distance. First and second hole pairs 44 and 46 may be one, two, three or more holes each. When multiple holes are utilized, they may be spaced symmetrically or asymmetrically. First ball pair 48 is disposed within first hole pair 44 while second ball pair 50 is disposed within second hole pair 46.

[0016] Partially hollow interior volume 52 of drive spindle 38 contains plunger 54. Plunger 54 provides first tapered end 56 and second tapered end 58. Reset spring 60 couples to plunger 54 at second tapered end 58. Reset spring 60 biases plunger 54. First ball pair 48 contacts first tapered end 56 of plunger 54, while second ball pair 50 contacts second tapered end 58 of plunger 54. Inertial device 62 couples to drive spindle 38 near first hole pair 44. Inertial device 62 contacts first ball pair 48 positioned within first hole pair 44.

[0017] Driven clutch member 34 provides ring gear 72 for driving a gear set. Ring gear 72 of driven clutch member 34 may directly drive planetary gears and planet carrier at the rotational speed of drive spindle 38. One-way clutch 78 allows driven clutch member 34, having ring gear 72, to rotate in only one direction. One-way clutch 78 may be a sprag clutch or any other device for allowing movement in one direction.

[0018] FIGURE 3 shows a cross-sectional view of inertial device 62 in which rotatably-driven, torque-responsive, gear shift device 30 is in engaged mode as shown in FIGURE 2. Inertial device 62 may include dowel pin 90, first disc 92, and second disc 94. Other types of inertial devices could be used with some aspects of the present invention, such as the inertial device shown in U.S. Patent 4,359,107, entitled "Shut-Off Apparatus for Pneumatic Driven Tools". FIGURE 3 also illustrates plunger 54, first ball pair 48, and first tapered end 56. Inertial device 62 contacts and retains first ball pair 48. First disc 92 and second disc 94 couple to drive spindle 38 by dowel pins (not shown). First disc 92 and second disc 94 are eccentric with respect to the axis of rotation of drive spindle 38. Therefore, rotation of drive spindle 38 causes first disc 92 and second disc 94 to force first ball pair 48 radially inward. First ball pair 48 exerts inward force upon plunger 54 at first tapered end 56. The radially inward force exerted on first tapered end 56 translates into an axial or longitudinal force on plunger 54 towards second tapered end 58 and driven clutch member 34.

[0019] FIGURE 4 illustrates rotatably-driven, torque-responsive, gear shift device 30 as shown in FIGURE 2 except with drive clutch member 32 disengaged from driven clutch member 34 (the disengaged mode). The description of FIGURE 2 applies equally here except that gear shift device 30 is in disengaged mode. FIGURE 4 shows rotatably-driven, torque-responsive, gear shift device 30 in a disengaged mode or low speed/high torque mode. As will be described in more detail later, the shift device 30 shifts from the engaged mode to the disengaged mode in response to a desired resistive torque applied at the output. In the disengaged mode, torque spring 40 is shown more compressed than in FIGURE 2, and drive clutch member 32 is shown longitudinally or axially displaced from driven clutch member 34. Inner axial groove 36 aligns with second hole pair 46, allowing second ball pair 50 to occupy inner axial groove 36. Inertial device 62 contacts first ball pair 48, shown radially displaced inwardly and contacting plunger 54 at first tapered end 56. Plunger 54 is axially or longitudinally displaced towards second tapered end 58 and compresses reset spring 60. The disengagement of drive clutch member 32 from driven clutch member 34 allows drive spindle 38 at second end 68, serving as pinion gear 70, to directly drive first reduction idler gear 74. During disengagement, one way clutch 78 prevents ring gear 72 from rotating in the opposite direction.

[0020] FIGURE 5 illustrates inertial device 62, also shown in FIGURE 3, except with rotatably-driven, torque-responsive, gear shift device 30 in disengaged mode as shown in FIGURE 4. First disc 92 and second disc 94 apply a radially inward force on first ball pair 48 and inwardly displace first ball pair 48. First ball pair 48 contacts plunger 54 at first tapered end 56 to apply a force thereto.

[0021] FIGURE 6 further illustrates ball screw arrangement 64 showing the ball screw interconnection between drive spindle 38 and drive clutch member 32. Ball keys 102 are shown as movably positioned in ball screw keyways 104. Ball screw arrangement 64 drivably engages drive clutch member 32 and drive spindle 38 in response to rotation. When a resistive torque applied to rotating drive spindle 38 overcomes the compression of torque spring 40, ball keys 102 will have moved in ball screw keyways 104 sufficiently to result in drive clutch member 32 being axially displaced away from driven clutch member 34. Ball screw arrangement 64 may be any arrangement that allows drive clutch member 32 to move axially or longitudinally along drive spindle 38. FIGURE 7 illustrates ball screw keyway 104 positioned on drive spindle 38. FIGURE 8 is a cross-sectional view of ball screw keyways 104 and drive spindle 38 taken along line 8-8 in FIGURE 7. Ball screw keyway 104 has a first end 101 and a second end 103.

[0022] In operation, the gear shift device changes gears in response to an applied resistive torque and shifts from an output rotational motion having a relative high speed/low torque to an output rotational motion having relative low speed/high torque. This occurs when shifting from engaged mode to disengaged mode.

[0023] In the one embodiment shown, the gear shift device 30 may operate according to the following steps. Referring to FIGURE 2, before any rotation of drive spindle 38, drive clutch member 32 engages driven clutch member 34 of rotatably-driven, torque-responsive, gear shift device 30. Drive clutch member 32 and drive spindle 38 are drivably engaged by ball screw arrangement 64 with ball keys 102 nearest first end 101 and hence are in engaged mode or high speed/low torque mode. This arrangement allows drive clutch member 32, drive spindle 38, and driven clutch member 34, to rotate together.

[0024] Reset spring 60 couples to plunger 54 at second tapered end 58. The arrangement of reset spring 60 and plunger 54 resists axial or longitudinal movement of plunger 54 towards reset spring 60, as shown in FIGURES 2 and 4. Reset spring 60 may couple to plunger 54 at other locations on plunger 54 and achieve the same effect. For example, reset spring 60 may be positioned concentrically around plunger 54 or attached at first tapered end 56. Second ball pair 50 contact plunger 54 around second tapered end 58 while remaining disposed in second hole pair 46. First ball pair 48 contact plunger 54 near first tapered end 56 while first ball pair 48 remains disposed in first hole pair 44. Although this embodiment shows a first ball pair 48 disposed in first hole pair 44, one ball disposed in one hole would probably provide the same effect as would multiple balls each disposed in a corresponding hole.

[0025] Drive spindle 38 couples to motor drive 86 and provides rotational motion thereto when energized. The rotational motion of motor drive 86 rotates drive spindle 38 and hence rotates drivably engaged drive clutch member 32. Torque spring 40 rotates with drive spindle 38 and drive clutch member 32.

[0026] Inertial device 62 couples to drive spindle 38 and applies a radially inward force on first ball pair 48 in response to rotation. The radially inward force applied to ball pair 48 forces ball pair 48, disposed in first hole pair 44 of drive spindle 38, into first tapered end 56 of plunger 54. First tapered end 56 translates this radially inward force to an axial or longitudinal force directed towards reset spring 60. The translation of a radially inward force to a longitudinal force on plunger 54 may be accomplished through using first tapered end 56 of plunger 54 as shown in FIGURES 2 and 4 or by any other known method of translating a force in one direction to another direction. Plunger 54 forces second ball pair 50 through second hole pair 46 and into inner axial groove 36 of drive clutch member 32 because second tapered end 58 of plunger 54 translates this axial or longitudinal force on plunger 54 into a radially outward force on second ball pair 50. Second ball pair 50 resists the radially outward force by contacting drive clutch member 32. Second ball pair 50 cannot enter inner axial groove 36 because inner axial groove 36 is not positioned around second hold pair 46 when drive clutch member 32 is engaged to driven clutch member 34.

[0027] A resistive torque acts on the output of drive spindle 38 that resists the rotation of drive spindle 38. The rotation is a result of motor drive 86 rotating drive spindle 38. When the resistive torque reaches a level that overcomes torque spring 40, torque spring 40 will have compressed sufficiently to disengage drive clutch member 32. While torque spring 40 compresses, ball screw arrangement 64, having ball keys 102 and ball screw keyway 104 shown in FIGURES 6-8, forces drive clutch member 32 into torque spring 40 and away from driven clutch member 34. Drive clutch member 32 moves axially or longitudinally along drive spindle 38 while compressing torque spring 40.

[0028] After sufficient movement between the ball key arrangement 64, the radially outward force acting on second ball pair 50 will force second ball pair 50 into inner axial groove 36 of drive clutch member 32. The movement of second ball pair 50 into inner axial groove 36 of drive clutch member 32 allows plunger 54 to compress reset spring 60. The axial or longitudinal movement of plunger 54, in response to the radially inward force of first ball pair 48, allows first ball pair 48 to move radially inward while maintaining contact with first tapered end 56 of plunger 54.

[0029] Inertial device 62 continues to apply a radially inward force on first ball pair 48 and hence on first tapered end 56 of plunger 54 until rotation of rotatably-driven, torque-responsive, gear shift device 30 stops. This ensures that plunger 54 continues to compress reset spring 60 and hence maintain second ball pair 50 in inner axial groove 36 of drive clutch member 32 until all rotation of drive spindle 38 ceases. Displacement of second ball pair 50 into the inner axial groove 36 or other slots prevents drive clutch member 32 from engaging driven clutch member 34 as shown in FIGURE 4 once it has disengaged. This ensures an output rotation having relative low speed/high torque.

[0030] During engagement of drive clutch member 32 and driven clutch member 34, ring gear 72 of driven clutch member 34 may directly drive planetary gears and a planet carrier at the rotational speed of drive spindle 38 and hence produce an output rotation having high speed/low torque. This is clearly shown in FIGURE 2. The disengagement of drive clutch member 32 from driven clutch member 34, shown in FIGURE 4, allows drive spindle 38 at second end 68, serving as pinion gear 70, to directly drive first reduction idler gear 74. One way clutch 78 prevents ring gear 72 from rotating in the opposite direction during disengagement.

[0031] Inertial device 62 is shown in FIGURE 3 with drive clutch member 32 and driven clutch member 34 engaged. Plunger 54 has not yet been axially or longitudinally displaced in FIGURE 3. FIGURE 3 shows first ball pair 48 before motor drive 86 applies rotation tc drive spindle 38 and hence the power tool is at rest or after motor drive 86 rotates drive spindle 38 and drive clutch member 32 continues to engage driven clutch member 34.

[0032] In the embodiment of inertial device 62 shown in FIGURE 3, first disc 92 and second disc 94 couple to drive spindle 38 near first tapered end 56 by dowel pins (not shown) and pivotally couple to one another through dowel pin 90 and dowel slot 96. Rotation of drive spindle 38 causes first disc 92 and second disc 94 to rotate with respect to drive spindle 38 and with respect to one another through dowel slot 96 and dowel pin 90. The resulting movement of first disc 92 and second disc 94 applies a radially inward force on first ball pair 48 which in turn translates to an axial or longitudinal force on plunger 54 through first tapered end 56. Inertial device 62 may be modified to apply a radially inward force to a single ball or to a plurality of balls disposed in corresponding holes.

[0033] Once drive clutch member 32 and driven clutch member 34 disengage, as shown in FIGURE 4, inertial device 62 prevents plunger 54 from moving axially or longitudinally away from reset spring 60 by continuously applying a radially inward force on first ball pair 48. Hence, drive clutch member 32 and driven clutch member 34 remain disengaged until all rotation stops and inertial device 62 allows reset spring 60 to axially or longitudinally force plunger 54 away from driven clutch member 34 by allowing first tapered end 56 to force first ball pair 48 radially outward and resetting inertial device 62 as shown in the embodiment illustrated in FIGURE 3.

[0034] An important aspect of the present invention and particularly inertial device 62 includes preventing a gear shifting power tool from shifting from a relative low speed/high torque output condition back into a relative high speed/low torque output condition before the proper high torque has been applied at the output. This ensures proper tightening of fasteners and proper application of a relative high torque.

[0035] Because the invention prevents rotatably-driven, torque-responsive, gear shift device 30 from shifting back into the engaged mode, the present invention provides safer operation of gear shifting power tools by preventing tool slippage as a result of undesirable and unexpected automatic gear shifts. The ability to deliver both high speed/low torque output and low speed/high torque output through the use of an automatic gear shifting device allows the use of a lower rpm motor which may allow the use of an oil free motor. When the motor driving the gear shifting power tool is a pneumatic motor or fluid driven motor, the automatic gear shifting power tool allows for a reduction in air or fluid consumption and hence reduced noise levels and cost.

[0036] The present invention allows for the selection of a torque at which gear shifting is desired by adjusting the compression on torque spring 40 through the positioning of adjustment nut 42 in the embodiment shown in the FIGURES. This may also be accomplished through the desired sizing of torque spring 40. The self-contained operation of the gear shifting power tool allows for power tools with reduced size and weight.

[0037] The present invention does not use any external fluids to apply pressure to engage and disengage clutch members. The absence of reliance on external fluids increases reliability and enhances responsiveness to applied torques. Finally, the use of ball screw arrangement 64 and having ball keys 102 and ball screw keyway 104, allows for full and complete disengagement of drive clutch member 32 from driven clutch member 34 which reduces internal frictional wear and increases reliability.

[0038] Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made therein without departing from the scope of the invention as defined by the appended claims.

Claims

1. A rotatably-driven, torque-responsive, gear shift device (30) for use in a power tool (10), the gear shift device comprising:

a drive spindle (38) having an axis, a first end (66), a second end (68), and a partially hollow interior volume (52), the drive spindle (38) being able to input, in use, a rotational force from a motor;

a drive clutch member (32) drivably engaged to the drive spindle (38) and movable along the axis of the drive spindle (38);

a biasing means (40) between the drive spindle (38) and the drive clutch member (32) allowing, in use, an axial movement of the drive clutch member (32) relative to the drive spindle (38) when the biasing load of the biasing means (40) is overcome;

a plunger (54) positioned within the partially hollow interior volume (52) of the drive spindle (38) and movable, in use, towards the second end of the drive spindle (68) to engage the drive clutch member (32) when the drive clutch member (32) has axially moved relative to the drive spindle (38) for changing the gearing of the gear shift device (30);

a reset biasing means (60) for biasing the plunger (54) in the partially hollow interior volume (52) of the drive spindle (38) away from the second end (68) to move the drive spindle (38) away from the second end (68) when the gear device (30) is not in use; and

an inertial device (62) coupled to the drive spindle (38) such that, in use, it urges the plunger (54) towards the second end (68) of the drive spindle (38) in response to rotation of the drive spindle (38).

2. The gear shift device (30) of claim 1, wherein the drive spindle (38) has a first hole (44) and second hole (46), and further comprising a first ball (48) movably positioned within the first hole (44) and contacting the plunger (54) near a first tapered end (56), and a second ball (50) movably positioned within the second hole (46) and contacting the plunger (54) near a second tapered end (58).

3. A gear shift device according to claim 1, wherein the drive spindle (38) has a first hole (44) and a second hole (46); the plunger (54) has a first tapered end (56) and a second tapered end (58); and the reset biasing means (60) is coupled to the second tapered end (58) of the plunger (54); the device (30) further comprising a first ball (48) movably positioned within the first hole (44) of the drive spindle (38) and contacting the plunger (54) near the first tapered end (56); a second ball (50) movably positioned within the second hole (46) of the drive spindle and contacting the plunger (54) near the second tapered end (58); wherein the inertial device (62) is coupled to the drive spindle (38) near the first hole (44) and in contact with the first ball (48); and the drive clutch member (32) has an inner axial groove (36) for receiving a portion of the second ball (50).

4. The gear shift device (30) of any of the preceding claims, wherein the drive spindle (38) has a first pair of holes (44) spaced about 180 degrees on the drive spindle, and a second pair of holes (46) spaced about 180 degrees on the drive spindle, and further comprising a first pair of balls (48) movably positioned within the first pair of holes and contacting the plunger (54) near the first tapered end (56), and a second pair of balls (50) movably positioned within the second pair of holes (46) and contacting the plunger (54) near the second tapered end (58).

5. The gear shift device (30) of any of the preceding claims, wherein the second end (68) of the drive spindle (38) is operable as a pinion for a gear set (70).

6. The gear shift device (30) of any of the preceding claims, further comprising a driven clutch member (34) having a ring gear (72) and engagable with the drive clutch member (32).

7. The gear shift device (30) of claim 6 further comprising a one-way clutch (78) allowing rotation of the driven clutch member (34) in one direction.

8. The gear shift device (30) of claim 7, wherein the one-way clutch (78) is a sprag clutch.

9. The gear shift device (30) of any of the preceding claims, wherein the drive clutch member (32) is driveably engaged to the drive spindle (38) through a ball screw arrangement (64).

10. The gear shift device (30) of any of the preceding claims, wherein the inertial device (62) comprises a first eccentric shaped disc (92) mounted on the drive spindle (38); and a second eccentric shaped disc (94) mounted on the drive spindle (38) about 180 degrees away from the first eccentric shaped disc (92) and pivotally coupled to the first eccentric disc (92) to provide a force on the plunger (54) in response to rotational motion.

11. The gear shift device (30) of any of the preceding claims, wherein the biasing means (40) is a torque spring.

12. The gear shift device (30) of any of the preceding claims, wherein the drive spindle (38) has first holes (44) and second holes (46), and further comprising a first plurality of balls (48) movably positioned within the first holes (44) and contacting the plunger (54) near the first tapered end (56), and a second plurality of balls (50) movably positioned within the second holes (46) and contacting the plunger (54) near the second tapered end (58).

13. The gear shift device (30) of any of the preceding claims, wherein the drive spindle (38) has a cylindrical shape.

14. The gear shift device (30) of any of the preceding claims, wherein the plunger (54) has a cylindrical shape.

15. The gear shift device (30) of any of the preceding claims, wherein the reset biasing means (60) is a spring.

16. The gear shift device (30) of any of the preceding clams, wherein the ball screw arrangement (64) comprises a plurality of interfitting ball keys (102) and keyways (104) which tends to axially separate the drive clutch member (32) from the driven clutch member (34) in response to a resistive torque on the drive spindle (38).

17. A gear shifting power tool (10) comprising:

a casing (13); a motor (86) disposed within the casing (13); and a rotatably-driven, torque responsive, gear shift device (30) according to any of claims 1 to 16, having a first end (66) rotatably coupled to the motor (86) and a second end (68).

18. A method for shifting gears, in response to an applied resistive torque, from an output rotational motion having relative high speed and low torque to an output rotational motion having relative low speed and high torque, the method comprising the steps of engaging a drive clutch member (32) to a driven clutch member (34) where the drive clutch member has an inner axial groove (36) and is drivably engaged to a drive spindle (38) having a partially hollow interior volume (52), a first hole (44), a second hole (46), a first end (66), and a second end (68); biasing a plunger (54) longitudinally away from the second end of the drive spindle where the plunger is positioned in the partially hollow interior volume of the drive spindle and contains a first tapered end (56) and a second tapered end (58); rotating the drive spindle (38) with a motor (86); applying a radially inward force to a first ball (48) tending to force the first ball radially inward through the first hole (44) towards plunger (54) to provide a longitudinal force on the plunger (54) opposite the biasing applied to the plunger (54) in the step of biasing a plunger (54) longitudinally; applying a torque to the drive spindle (38) that resists the rotation of the drive spindle (38) produced by the motor (86); disengaging the drive clutch member (32) from the driven clutch member (34) in response to the step of applying a torque to the drive spindle (38) that resists the rotation of the drive spindle (38) by compressing a spring (40) between the drive clutch member (32) and the drive spindle (34) so that the drive clutch member (32) moves longitudinally away from the driven clutch member (34) and the inner axial groove (36) positions over the second hole (46) in the drive spindle (38); moving the plunger (54) longitudinally towards the second end (68) of the drive spindle (38) in response to the step of applying a radially inward force on the first ball (48) and the step of disengaging the drive clutch member (32) from the driven clutch member (34); and forcing a second ball (50) radially outward through the second hole (46) of t:he drive spindle (38) and into the inner axial groove (31) of the drive clutch member (32) in response to moving the plunger (52) longititudinally towards the second end (68) of the drive spindle (38).

19. The method of claim 18, wherein the drive spindle (38) has a first end (66) and a second end (66) and the second end is operable as a pinion (70) of a gear set.

20. The method of claim 19, wherein the second end (68) of the drive spindle (38) is the pinion for a planetary gear set.

21. The method of claim 18, wherein the drive clutch member (34) has a ring gear (70) for driving a gear set.

22. The method of claim 18, wherein the step of applying a radially inward force to a first ball (48) includes applying the radially inward force with an inertial device (62) having a first eccentric shaped disc (92) mounted on the drive spindle (38) and a second eccentric shaped disc (94) mounted on the drive spindle (38) about 180 degrees away from the first eccentric shaped disc (92) and pivotally coupled to the first eccentric disc (92) to provide the radially inward force on the first ball (48) in response to rotational motion.

23. The method of claim 18, wherein the step of disengaging the drive clutch member (32) from the driven clutch member (34) includes the drive clutch member (32) being drivably engaged to the drive spindle (38) through a ball screw arrangement (64) and wherein the drive clutch member (32) moves longitudinally away from the driven clutch member (34) in response to the step of applying a torque to the drive spindle (38) that resists the rotation of the drive spindle (38).

Ansprüche

1. Drehend angetriebene, auf Drehmoment ansprechende Gangschaltungsvorrichtung (30) zum Einsatz in einem elektrischen Werkzeug (10), wobei die Gangschaltungsvorrichtung umfasst:

eine Antriebsspindel (38) mit einer Achse, einem ersten Ende (66), einem zweiten Ende (68) und einem teilweise hohlen Innenraum (52), wobei die Antriebsspindel (38) in Funktion eine Drehkraft von einem Motor einleiten kann;

ein Antriebskupplungselement (32), das antreibend mit der Antriebsspindel (38) in Eingriff ist und auf der Achse der Antriebsspindel (38) entlang bewegt werden kann;

eine Spanneinrichtung (40) zwischen der Antriebsspindel (38) und dem Antriebskupplungselement (32), die in Funktion eine axiale Bewegung des Antriebskupplungselementes (32) gegenüber der Antriebsspindel (38) ermöglicht, wenn die Spannkraft der Spanneinrichtung (40) überwunden wird;

einen Kolben (54), der in dem teilweise hohlen Innenraum (52) der Antriebsspindel (38) angeordnet ist und in Funktion auf das zweite Ende der Antriebsspindel (38) zu bewegt werden kann, um mit dem Antriebskupplungselement (32) in Eingriff zu kommen, wenn sich das Antriebskupplungselement (32) in Bezug auf die Antriebsspindel (38) axial bewegt hat, um die Übersetzung der Gangschaltungsvorrichtung (30) zu ändern;

eine Rücksetz-Spanneinrichtung (60), die den Kolben (54) in dem teilweise hohlen Innenraum (52) der Antriebsspindel (38) von dem zweiten Enden (68) weg spannt, um die Antriebsspindel (38) von dem zweiten Ende (68) weg zu bewegen, wenn die Gangschaltungsvorrichtung (30) nicht in Funktion ist; und

eine Tragheitsvorrichtung (62), die mit der Antriebsspindel (38) so verbunden ist, dass sie in Funktion den Kolben (54) in Reaktion auf Drehung der Antriebsspindel (38) auf das zweite Ende (68) der Antriebsspindel (38) zu drückt.

2. Gangschaltungsvorrichtung (30) nach Anspruch 1, wobei die Antriebsspindel (38) ein erstes Loch (44) und ein zweites Loch (46) aufweist und des Weiteren eine erste Kugel (48), die beweglich in dem ersten Loch (44) angeordnet und mit dem Kolben (54) in der Nähe eines ersten sich verjüngenden Endes (56) in Kontakt ist, sowie eine zweite Kugel (50) umfasst, die beweglich in dem zweiten Loch (46) angeordnet und in der Nähe eines zweiten sich verjüngenden Endes (58) mit dem Kolben (54) in Kontakt ist.

3. Gangschaltungsvorrichtung nach Anspruch 1, wobei die Antriebsspindel (38) ein erstes Loch (44) und ein zweites Loch (46) aufweist, der Kolben (54) ein erstes sich verjüngendes Ende (56) und ein zweites sich verjüngendes Ende (58) aufweist und die Rücksetz-Spanneinrichtung (60) mit dem zweiten sich verjüngenden Ende (58) des Kolbens (54) verbunden ist, wobei die Vorrichtung (30) des Weiteren eine erste Kugel (48), die beweglich in dem ersten Loch (44) der Antriebsspindel (38) angeordnet und in der Nähe des ersten sich verjüngenden Endes (56) mit dem Kolben (54) in Kontakt ist; eine zweite Kugel (50) umfasst, die beweglich in dem zweiten Loch (46) der Antriebsspindel angeordnet und in der Nähe des zweiten sich verjüngenden Endes (58) mit dem Kolben (54) in Kontakt ist; wobei die Tragheitsvorrichtung (62) in der Nähe des ersten Lochs (44) mit der Antriebsspindel (38) verbunden und mit der ersten Kugel (48) in Kontakt ist, und das Antriebskupplungselement eine innere axiale Nut (36) hat, die einen Teil der zweiten Kugel (50) aufnimmt.

4. Gangschaltungsvorrichtung (30) nach einem der vorangehenden Ansprüche, wobei die Antriebsspindel (38) ein erstes Paar Löcher (44), die um 180° beabstandet an der Antriebsspindel angeordnet sind, sowie ein zweites Paar Löcher (46) aufweist, die um 180° beabstandet an der Antriebsspindel angeordnet sind, und die des Weiteren ein erstes Paar Kugeln (48), die beweglich in dem ersten Paar Löcher angeordnet und in der Nähe des ersten sich verjüngenden Endes (56) mit dem Kolben (54) in Kontakt sind, und ein zweites Paar Kugeln (50) umfasst, die beweglich in dem zweiten Paar Löcher (46) angeordnet und in der Nähe des zweiten sich verjüngenden Endes (58) mit dem Kolben (54) in Kontakt sind.

5. Gangschaltungsvorrichtung (30) nach einem der vorangehenden Ansprüche, wobei das zweite Ende (68) der Antriebsspindel (38) als ein Ritzel für einen Zahnradsatz (70) betrieben werden kann.

6. Gangschaltungsvorrichtung (30) nach einem der vorangehenden Ansprüche, die des Weiteren ein angetriebenes Kupplungselement (34) umfasst, das ein Innenzahnrad (72) aufweist und mit dem Antriebskupplungselement (32) in Eingriff gebracht werden kann.

7. Gangschaltungsvorrichtung (30) nach Anspruch 6, die des Weiteren eine Freilaufkupplung (78) umfasst, die Drehung des angetriebenen Kupplungselementes (34) in einer Richtung ermöglicht.

8. Gangschaltungsvorrichtung (30) nach Anspruch 7, wobei die Freilaufkupplung (78) eine Klemmkörper-Freilaufkupplung ist.

9. Gangschaltungsvorrichtung (30) nach einem der vorangehenden Ansprüche, wobei das Antriebskupplungselement (32) antreibend über eine Kugelspindelanordnung (64) mit der Antriebsspindel (38) in Eingriff ist.

10. Gangschaltungsvorrichtung (30) nach einem der vorangehenden Ansprüche, wobei die Trägheitsvorrichtung (62) eine erste exzentrisch geformte Scheibe (92) die an der Antriebsspindel (38) angebracht ist, sowie eine zweite exzentrisch geformte Scheibe (94) umfasst, die um 180° von der ersten exzentrisch geformten Scheibe (92) entfernt an der Antriebsspindel (38) angebracht und mit der ersten exzentrischen Scheibe (92) schwenkbar verbunden ist, um in Reaktion auf Drehbewegung eine Kraft auf den Kolben (54) auszuüben.

11. Gangschaltungsvorrichtung (30) nach einem der vorangehenden Ansprüche, wobei die Spanneinrichtung (40) eine Torsionsfeder ist.

12. Gangschaltungsvorrichtung (30) nach einem der vorangehenden Ansprüche, wobei die Antriebsspindel (38) erste Löcher (44) und zweite Löcher (46) aufweist und des Weiteren eine erste Vielzahl von Kugeln (48), die beweglich in den ersten Löchern (44) angeordnet und in der Nähe des ersten sich verjüngenden Endes (56) mit dem Kolben (54) in Kontakt sind, und eine zweite Vielzahl von Kugeln (50) umfasst, die beweglich in den zweiten Löchem (46) angeordnet und in der Nähe des zweiten sich verjüngenden Endes (58) mit dem Kolben (54) in Kontakt sind.

13. Gangschaltungsvorrichtung (30) nach einem der vorangehenden Ansprüche, wobei die Antriebsspindel (38) eine zylindrische Form hat.

14. Gangschaltungsvorrichtung (30) nach einem der vorangehenden Ansprüche, wobei der Kolben (54) eine zylindrische Form hat.

15. Gangschaltungsvorrichtung (30) nach einem der vorangehenden Ansprüche, wobei die Rücksetz-Spanneinrichtung (60) eine Feder ist.

16. Gangschaltungsvorrichtung (30) nach einem der vorangehenden Ansprüche, wobei die Kugelspindelanordnung (64) eine Vielzahl ineinanderpassender Kugelkeile (102) und Keilnuten (104) umfasst, die das Antriebskupplungselement (32) in Reaktion auf ein Widerstandsdrehmoment von der Antriebsspindel (38) axial von dem angetriebenen Kupplungselement (34) trennen.

17. Gangschaltungs-Elektrowerkzeug (10), das umfasst:

eine Verkleidung (13); einen Motor (86), der in der Verkleidung (13) angeordnet ist, sowie eine drehend angetriebene, auf Drehmoment ansprechende Gangschaltungsvorrichtung (30) nach einem der Ansprüche 1 bis 16, die ein erstes Ende (66), das drehbar mit dem Motor (86) verbunden ist, und ein zweites Ende (68) aufweist.

18. Verfahren zum Gangschalten in Reaktion auf ein wirkendes Widerstandsdrehmoment von einer Ausgangsdrehbewegung mit einer relativ hohen Geschwindigkeit und einem geringen Drehmoment auf eine Ausgangsdrehbewegung mit einer relativ niedrigen Geschwindigkeit und einem hohen Drehmoment, wobei das Verfahren die Schritte des Ineingriffbringens eines Antriebskupplungselementes (32) mit einem angetriebenen Kupplungselement (34), wobei das Antriebskupplungselement eine innere axiale Nut (36) aufweist und antreibend mit einer Antriebsspindel (38) in Eingriff ist, die einen teilweise hohlen Innenraum (52), ein erstes Loch (44), ein zweites Loch (46), ein erstes Ende (66) und ein zweites Ende (68) aufweist; des Spannens eines Kolbens (54) in Längsrichtung von dem zweiten Ende der Antriebsspindel weg, wobei der Kolben in dem teilweise hohlen Innenraum der Antriebsspindel angeordnet ist und ein erstes sich verjüngendes Ende (56) und ein zweites sich verjüngendes Ende (58) enthält, des Drehens der Antriebsspindel (38) mit einem Motor (86), des Ausübens einer radial nach innen gerichteten Kraft auf eine erste Kugel (48), durch die die erste Kugel radial nach innen durch das erste Loch (44) hindurch auf den Kolben (54) zu gedrückt wird und eine Längskraft auf den Kolben (54) entgegengesetzt zu der auf den Kolben (54) beim Schritt des Spannens eines Kolbens (54) in Längsrichtung ausgeübten Spannung ausübt; des Ausübens eines Drehmomentes auf die Antriebsspindel (38), das der Drehung der Antriebsspindel (38) Widerstand entgegengesetzt, die durch den Motor (86) erzeugt wird; des Trennens des Antriebskupplungselementes (32) von dem angetriebenen Kupplungselement (34) in Reaktion auf den Schritt des Ausübens eines Drehmomentes auf die Antriebsspindel (38), das der Drehung durch die Antriebsspindel (38) Widerstand entgegensetzt, durch Zusammendrücken einer Feder (40) zwischen dem Antriebskupplungselement (32) und der Antriebsspindel (34), so dass sich das Antriebskupplungselement (32) in Längsrichtung axial von dem angetriebenen Kupplungselement (34) weg bewegt und die innere axiale Nut (36) über dem zweiten Loch (46) in der Antiebsspindel (38) angeordnet wird; des Bewegens des Kolbens (54) in Längsrichtung auf das zweite Ende (68) der Antriebsspindel (38) zu in Reaktion auf den Schritt des Ausübens einer radial nach innen gerichteten Kraft auf die erste Kugel (38) und den Schritt des Lösens des Antriebskupplungselementes (32) von dem angetriebenen Kupplungselement (34); und des Drückens einer zweiten Kugel (50) radial nach außen durch das zweite Loch (46) der Antriebsspindel (38) hindurch und in die innere axiale Nut (31) des Antriebskupplungselementes (32) hinein in Reaktion auf das Bewegen des Kolbens (52) in Längsrichtung auf das zweite Ende (68) der Antriebsspindel (38) zu umfasst.

19. Verfahren nach Anspruch 18, wobei die Antriebsspindel (38) ein erstes Ende (66) und ein zweites Ende (66) aufweist und das zweite Ende als ein Ritzel (70) eines Zahnradsatzes betrieben kann.

20. Verfahren nach Anspruch 19, wobei das zweite Ende (68) der Antriebsspindel (38) das Ritzel für einen Planetenradsatz ist.

21. Verfahren nach Anspruch 18, wobei das Antriebskupplungselement (34) ein Innenzahnrad (70) zum Antreiben eines Zahnradsatzes aufweist.

22. Verfahren nach Anspruch 18, wobei der Schritt des Ausübens einer radial nach innen gerichteten Kraft auf eine erste Kugel (48) das Ausüben der radial nach innen gerichteten Kraft mit einer Trägheitsvorrichtung (62) einschließt, die eine erste exzentrisch geformte Scheibe (92), die an der Antriebsspindel (38) angebracht ist, und eine zweite exzentrisch geformte Scheibe (94) aufweist, die um 180° von der ersten exzentrisch geformten Scheibe (92) entfemt an der Antriebsspindel (38) angebracht und schwenkbar mit der ersten exzentrischen Scheibe (92) verbunden ist, um in Reaktion auf Drehbewegung die radial nach innen gerichtete Kraft auf die erste Kugel (48) auszuüben.

23. Verfahren nach Anspruch 18, wobei der Schritt des Trennens des Antriebskupplungselementes (32) von dem angetriebenen Kupplungselement (34) einschließt, dass das Antriebskupplungselement (32) über eine Kugelspindelanordnung (64) antreibend mit der Antriebsspindel (38) in Eingriff gebracht wird, und wobei sich das Antriebskupplungselement (32) in Reaktion auf den Schritt des Ausübens eines Drehmomentes auf die Antriebsspindel (38), das der Drehung der Antriebsspindel (38) Widerstand entgegensetzt, in Längsrichtung von dem angetriebenen Kupplungselement (34) weg bewegt.

Revendications

1. Dispositif de changement de vitesse en fonction du couple entraîné en rotation (30) destiné à être utilisé dans un outil à moteur (10), le dispositif de changement de vitesse comprenant:

une broche d'entraînement (38) présentant un axe, une première extrémité (66), une seconde extrémité (68), et un volume intérieur partiellement creux (52), la broche d'entraînement (38) permettant d'introduire, en utilisation, un couple de rotation à partir d'un moteur ;

un élément d'embrayage d'entraînement (32) accouplé de manière à être entraîné avec la broche d'entraînement (38) et mobile suivant l'axe de la broche d'entraînement (38) ;

un moyen de rappel (40) entre la broche d'entraînement (38) et l'élément d'embrayage d'entraînement (32) permettant, en utilisation, un déplacement axial de l'élément d'embrayage d'entraînement (32) par rapport à la broche d'entraînement (38) lorsque la charge de rappel du moyen de rappel (40) est dépassée ;

un piston (54) positionné à l'intérieur du volume intérieur partiellement creux (52) de la broche d'entraînement (38) et pouvant être déplacé, en utilisation, vers la seconde extrémité de la broche d'entraînement (68) pour s'accoupler avec l'élément d'embrayage d'entraînement (32) lorsque l'élément d'embrayage d'entraînement (32) s'est déplacé axialement par rapport à la broche d'entraînement (38) afin de modifier le rapport de réduction du dispositif de changement de vitesse (30);

un moyen de rappel de repositionnement (60) destiné à appliquer une charge sur le piston (54) dans le volume intérieur partiellement creux (52) de la broche d'entraînement (38) à l'opposé de la seconde extrémité (68) afin de déplacer la broche d'entraînement (38) à l'opposé de la seconde extrémité (68) lorsque le dispositif de changement de vitesse (30) n'est pas en utilisation ; et

un dispositif inertiel (62) couplé à la broche d'entraînement (38) de telle sorte que, en utilisation, il pousse le piston (54) vers la seconde extrémité (68) de la broche d'entraînement (38) en réponse à la rotation de la broche d'entraînement (38).

2. Dispositif de changement de vitesse (30) selon la revendication 1, dans lequel la broche d'entraînement (38) présente un premier orifice (44) et un second orifice (46), et comprenant, en outre, une première bille (48) positionnée de manière à pouvoir se déplacer à l'intérieur du premier orifice (44) et venant en contact avec le piston (54) à proximité d'une première extrémité conique (56), une seconde bille (50) positionnée de manière à pouvoir se déplacer à l'intérieur du second orifice (46) et venant en contact avec le piston (54) à proximité d'une seconde extrémité conique (58).

3. Dispositif de changement de vitesse selon la revendication 1, dans lequel la broche d'entraînement (38) présente un premier orifice (44) et un second orifice (46) ; le piston (54) présente une première extrémité conique (56) et une seconde extrémité conique (58) ; et le moyen de repositionnement (60) est couplé à la seconde extrémité (58) du piston (54) ; le dispositif (30) comprenant, en outre, une première bille (48) positionnée de manière à pouvoir se déplacer à l'intérieur du premier orifice (44) de la broche d'entraînement (38) et venant en contact avec le piston (54) à proximité de la première extrémité conique (56) ;
   une seconde bille (50) positionnée de manière à pouvoir se déplacer à l'intérieur du second orifice (46) de la broche d'entraînement et venant en contact avec le piston (54) à proximité de la seconde extrémité conique (58) ; dans lequel le dispositif inertiel (62) est couplé à la broche d'entraînement (38) à proximité du premier orifice (44) et en contact avec la première bille (48) ; et l'élément d'embrayage d'entraînement (32) comporte une rainure axiale interne (36) afin de recevoir une partie de la seconde bille (50).

4. Dispositif de changement de vitesse (30) selon l'une quelconque des revendications précédentes, dans lequel la broche d'entraînement (38) présente une première paire d'orifices (44) espacés de 180 degrés environ sur la broche d'entraînement, et une seconde paire d'orifices (46) espacés de 180 degrés environ sur la broche d'entraînement, et comprenant, en outre, une première paire de billes (48) positionnées de manière à pouvoir se déplacer à l'intérieur de la première paire d'orifices et venant en contact avec le piston (54) à proximité de la première extrémité conique (56) et une seconde paire de billes (50) positionnées de manière à pouvoir se déplacer à l'intérieur de la seconde paire d'orifices (46) et venant en contact avec le piston ( 54) à proximité de la seconde extrémité conique (58).

5. Dispositif de changement de vitesse (30) selon l'une quelconque des revendications précédentes, dans lequel la seconde extrémité (68) de la broche d'entraînement (38) assure une fonction de pignon pour un jeu d'engrenages (70).

6. Dispositif de changement de vitesse (30) selon l'une quelconque des revendications précédentes, comprenant, en outre, un élément d'embrayage entraîné (34) présentant une couronne d'engrenage (72) et pouvant s'accoupler avec l'élément d'embrayage d'entraînement (32).

7. Dispositif de changement de vitesse (30) selon la revendication 6, comprenant, en outre, un embrayage unidirectionnel (78) permettant la rotation de l'élément d'embrayage entraîné (34) dans un sens.

8. Dispositif de changement de vitesse (30) selon la revendication 7, dans lequel l'embrayage unidirectionnel (78) est un embrayage à roue libre.

9. Dispositif de changement de vitesse (30) selon l'une quelconque des revendications précédentes, dans lequel l'élément d'embrayage d'entraînement (32) est accouplé de manière à être entraîné avec la broche d'entraînement (38) par l'intermédiaire d'un agencement formant vis à billes (64).

10. Dispositif de changement de vitesse (30) selon l'une quelconque des revendications précédentes, dans lequel le dispositif inertiel (62) comprend un premier disque de forme excentrée (92) monté sur la broche d'entraînement (38) ; et un second disque de forme excentrée (94) monté sur la broche d'entraînement (38) à 180 degrés environ à l'opposé du premier disque de forme excentrée (92) et couplé de manière à pouvoir pivoter par rapport au premier disque excentré (92) afin d'exercer un effort sur le piston (54) en réponse à un mouvement de rotation.

11. Dispositif de changement de vitesse (30) selon l'une quelconque des revendications précédentes, dans lequel le moyen de rappel (40) est un ressort de couple.

12. Dispositif de changement de vitesse (30) selon l'une quelconque des revendications précédentes, dans lequel la broche d'entraînement (38) présente des premiers orifices (44) et des seconds orifices (46), et comprenant, en outre, une première pluralité de billes (48) positionnées de manière à pouvoir se déplacer à l'intérieur des premiers orifices (44) et venant en contact avec le piston (54) à proximité de la première extrémité conique (56) et une seconde pluralité de billes (50) positionnées de manière à pouvoir se déplacer à l'intérieur des seconds orifices (46) et venant en contact avec le piston (54) à proximité de la seconde extrémité conique (58).

13. Dispositif de changement de vitesse (30) selon l'une quelconque des revendications précédentes, dans lequel la broche d'entraînement (38) présente une forme cylindrique.

14. Dispositif de changement de vitesse (30) selon l'une quelconque des revendications précédentes, dans lequel le piston (54) présente une forme cylindrique.

15. Dispositif de changement de vitesse (30) selon l'une quelconque des revendications précédentes, dans lequel le moyen de repositionnement (60) est un ressort.

16. Dispositif de changement de vitesse (30) selon l'une quelconque des revendications précédentes, dans lequel l'agencement formant vis à billes (64) comprend une pluralité de billes formant clavette (102) et de rainures (104) imbriquées qui tendent à séparer axialement l'élément d'embrayage d'entraînement (32) de l'élément d'embrayage entraîné (34) en réponse à un couple résistant sur la broche d'entraînement (38).

17. Outil à moteur à changement de vitesse (10), comprenant:

un boîtier (13), un moteur (86) disposé à l'intérieur du boîtier (13) ; et un dispositif de changement de vitesse en fonction du couple entraîné en rotation (30) selon l'une quelconque des revendications 1 à 16, présentant une première extrémité (66) couplée en rotation au moteur (86) et une seconde extrémité (68).

18. Procédé de changement de vitesse, en réponse à l'application d'un couple résistant, à partir d'un mouvement de rotation de sortie présentant une vitesse relativement élevée et un couple faible vers un mouvement de rotation de sortie présentant une vitesse relativement faible et un couple élevé, le procédé comprenant les étapes d'accouplement d'un élément d'embrayage d'entraînement (32) sur un élément d'embrayage entraîné (34) dans lequel l'élément d'embrayage d'entraînement comporte une rainure axiale interne (36) et est accouplé de manière à être entraîné avec une broche d'entraînement (38) présentant un volume intérieur partiellement creux (52), un premier orifice (44), un second orifice (46), une première extrémité (66) et une seconde extrémité (68) ; de rappel d'un piston (54), longitudinalement à l'opposé de la seconde extrémité de la broche d'entraînement, dans lequel le piston est positionné dans le volume intérieur partiellement creux de la broche d'entraînement et comprend une première extrémité conique (56) et une seconde extrémité conique (58) ; d'entraînement en rotation de la broche d'entraînement (38) avec un moteur (86) ; d'application d'un effort radialement vers l'intérieur sur une première bille (48) tendant à forcer la première bille radialement vers l'intérieur à travers le premier orifice (44) vers le piston (54) de manière à créer un effort longitudinal sur le piston (54) opposé à la charge initiale appliquée sur le piston (54) dans l'étape d'application de charge initiale longitudinale sur un piston (54) ; d'application d'un couple sur la broche d'entraînement (38) qui s'oppose à la rotation de la broche d'entraînement (38) produite par le moteur (86) ; de séparation de l'élément d'embrayage d'entraînement (32) par rapport à l'élément d'embrayage entraîné (34) en réponse à l'étape d'application d'un couple sur la broche d'entraînement (38) qui s'oppose à la rotation de la broche d'entraînement (38) en comprimant un ressort (40) entre l'élément d'embrayage d'entraînement (32) et la broche d'entraînement (34) de telle sorte que l'élément d'embrayage d'entraînement (32) se déplace longitudinalement à l'opposé de l'élément d'embrayage entraîné (34) et la rainure axiale interne (36) se positionne au-dessus du second orifice (46) dans la broche d'entraînement (38); de déplacement longitudinal du piston (54) vers la seconde extrémité (68) de la broche d'entraînement (38) en réponse à l'étape d'application d'un effort radialement vers l'intérieur sur la première bille (48) et à l'étape de séparation de l'élément d'embrayage d'entraînement (32) par rapport à l'élément d'embrayage entraîné (34) ; et d'application d'un effort sur une seconde bille (50) radialement vers l'intérieur à travers le second orifice (46) de la broche d'entraînement (38) et vers la rainure axiale interne (31) de l'élément d'embrayage d'entraînement (32) en réponse au déplacement longitudinal du piston (52) vers la seconde extrémité (68) de la broche d'entraînement (38).

19. Procédé selon la revendication 18, dans lequel la broche d'entraînement (38) présente une première extrémité (66) et une seconde extrémité (68) et la seconde extrémité peut fonctionner comme un pignon (70) d'un jeu d'engrenages.

20. Procédé selon la revendication 19, dans lequel la seconde extrémité (68) de la broche d'entraînement (38) est le pignon d'un jeu d'engrenages épicycloïdaux.

21. Procédé selon la revendication 18, dans lequel l'élément d'embrayage d'entraînement (34) présente une couronne d'engrenage (70) destinée à entraîner un jeu d'engrenages.

22. Procédé selon la revendication 18, dans lequel l'étape d'application d'un effort radialement vers l'intérieur sur une première bille (48) comprend l'application de l'effort radialement vers l'intérieur avec un dispositif inertiel (62) présentant un premier disque de forme excentrée (92) monté sur la broche d'entraînement (38) et un second disque de forme excentrée (94) monté sur la broche d'entraînement (38) à 180 degrés environ à l'opposé du premier disque de forme excentrée (92) et couplé de manière à pouvoir pivoter au premier disque excentré (92) afin de produire l'effort radialement vers l'intérieur sur la première bille (48) en réponse à un mouvement de rotation.

23. Procédé selon la revendication 18, dans lequel l'étape de séparation de l'élément d'embrayage d'entraînement (32) de l'élément d'embrayage entraîné (34) comprend l'accouplement de manière à assurer l'entraînement de l'élément d'embrayage d'entraînement (32) sur la broche d'entraînement (38) par l'intermédiaire d'un agencement formant vis à billes (64), et dans lequel l'élément d'embrayage d'entraînement (32) se déplace longitudinalement à l'opposé de l'élément d'embrayage entraîné (34) en réponse à l'étape d'application d'un couple sur la broche d'entraînement (38) qui s'oppose à la rotation de la broche d'entraînement (38).

Drawing